Resiliently deformable containers, often called "squeeze bottles", are in widespread use for a variety of fluid products for both home and industrial use. A typical deformable container rests on a flat bottom, and has a spout on top which may include any one of a number of available sealing arrangements. The fluid contents of the bottle are dispensed by inverting the bottle and squeezing it, reducing the effective interior space within the bottle and thus forcing the contents out of the spout.
In recent years there have been developed deformable dispensing containers which are inverted, i.e., in which the spout is located on or about the base of the bottle. An example of such a container is found in U.S. Pat. No. 5,037,005 issued Aug. 6, 1991, in which the spout is located on an inclined wall of the container adjacent to its base. The primary advantage of such a design, particularly in the case of viscous contents, is that the contents of the bottle are immediately available for dispensing through the spout, as opposed to an ordinary upright bottle in which the user inverts the bottle and then must wait until the contents flow toward the spout under the influence of gravity before the contents can be dispensed.
With the availability of inverted dispensing bottles there has arisen a need for a spout which is self-sealing. It is inconvenient to utilize manually closable sealing means on a spout in the case of an inverted dispenser, where immediate dispensing is one of its most attractive features. A self-sealing spout avoids this problem, but the design of a self-sealing spout can be particularly difficult to accomplish. Essentially, the spout must open and allow an egress of the fluid contents of the container under the pressure of manual squeezing, but must completely close so that the contents of the container do not continually leak out of the spout when the container is not being squeezed.
Moreover, venting in manually closeable spouts used in an inverted dispenser is typically inadequate. Because the contents in an inverted dispenser are immediately available for dispensing, the container may require an aperture that is larger than what would be necessary in a conventional dispensing bottle for contents of similar viscosity. Although the larger aperture may help venting, it will result in messy and poorly controlled dispensing.
One solution that has been proposed is described in U.S. Pat. No. 4,728,006 issued Mar. 1, 1988, which is incorporated herein by reference. The valve described in this patent comprises a horizontal flange adapted to be secured between the lip of an inverted bottle spout and a cap, and a diaphragm portion comprising an inwardly concave resilient dome having one or more slits in or about its apex. Because the dome is inwardly concave, when the bottle is in the rest position the pressure of the fluid contents of the bottle force the edges of the slit together. When the bottle is squeezed, the pressure becomes sufficient to force the diaphragm dome into an outwardly convex position, at which point the compressive force on the fluid forces the edges of the slit apart and the fluid contents of the bottle flow out of the slit. When the squeezing pressure is released the dome returns to its original concave position. This valve has proved to be very effective at selectively permitting the contents of a container to be dispensed without any leakage when the container is at rest.
However, the valve described in U.S. Pat. No. 4,728,006, although it dispenses fluid contents effectively, has very poor "venting", i.e., permitting an ingress of air back into the bottle once the squeezing force has been released, which allows the bottle to return to its original undeformed shape. In order to prevent leakage through the diaphragm when the bottle is at rest, the edges of the fluid egress slit must be designed to be forced together until the bottle is squeezed. As noted above the pressure of the fluid contents on the dome in its concave rest position force the edges of the slit together. This presents a considerable advantage in terms of preventing unwanted leakage from the bottle, but results in a significant disadvantage in the ability of the bottle to vent.
Particularly where a viscous fluid is being dispensed, once the squeezing pressure has been released the ingress of air through the slit is insufficient, and the bottle thus remains deformed for considerably longer than it should. This presents a hindrance when large amounts of fluid are desired, since the user must wait for the bottle to slowly return to its rest condition after each squeeze before the bottle can be squeezed again to dispense more fluid. Furthermore, the deformed bottle is not symmetrical in shape, and in some cases may not be stable and free-standing in a deformed condition, forcing the user to wait until the bottle has vented before replacing it on a table or shelf. Over time the bottle becomes permanently deformed as the walls become concave, so that it becomes increasingly difficult to squeeze the bottle and dispense its contents.
Thus, the container described in U.S. Pat. No. 4,728,006 is required to be made of certain materials, and shaped within certain design constraints, so that the walls have a very strong "return" or "memory", thus ensuring proper venting with viscous fluids.